Reference is made to my previously issued U.S. Pat. No. 3,706,344; 3,871,448; and to patent application Ser. No. 517,391; now U.S. Pat. No. 3,966,236; for further background of the invention.
In completing well bores, it is desirable to use a large casing-type gun which will efficiently perforate the casing and form passageways which extend a considerable distance back up into the formation, thereby gaining maximum potential production from the surrounding production zones. In order to satisfactorily carry out this desirable operation, it is necessary to connect the relatively large casing gun to a relatively smaller production tubing if production is to be carried out simultaneously with the firing of the gun. This expedient necessitates the employment of packer devices and vent strings along with the large casing gun. Should the gun misfire for one reason or another, a considerable amount of time and money is involved in bringing the entire tool string back to the surface of the ground where corrective action can be carried out in order to render the gun operative.
A gun will often misfire when it has been installed and left downhole for a substantial length of time prior to detonation. The usual cause of the misfire is an accumulation of debris layered over the firing head of the gun, or alternatively, a defective gun circuit. Therefore, if one could somehow determine the cause of the misfire, proper corrective action may be oftentimes employed, thereby making it unnecessary to bring the gun to the surface of the earth for correcting the cause of the misfire.
Therefore, it is desirable to have made available a well completion apparatus combined with a special wireline actuated tool wherein the tool can be run downhole in order that a determination can be made regarding the operable condition of a jet gun. At this time, it would be desirable for the wireline operator to be able to either fire the gun, or alternatively, bring the tool back out of the hole so that other tool strings can be run downhole to carry out various corrective actions upon the gun. On the other hand, should the gun be in proper condition for firing, it would accordingly be desirable to be able to fire the gun, permit the well to produce, while at the same time the gun is dropped to the bottom of the borehole and the tool removed from the producing well.